Where Does All the Garbage Go?
By “Awake!” correspondent in Japan
“HOW exasperating! All I was going to do was empty the dustpan, but the wastebasket spilled over. Now I have an even bigger mess!” At one time or another this may have happened to you. And it is what many large cities in the world are experiencing on a vast scale. Their garbage-disposal facilities are taxed to capacity.
This was a problem in the city of Numazu, Japan, in a very scenic area between stately Mount Fuji and Suruga Bay. The incinerator that had been built about 10 years earlier just could not cope with the demands put on it. A large portion of the garbage was only partially burned. Therefore, the ashes that were buried included much raw vegetable matter. What was the result? There was a tremendous expansion in the fly population.
When, for example, a truck driver started to dump some ashes from a factory, he noticed that the ground changed color. What appeared to be black topsoil was in reality a blanket of flies. Then, suddenly, the flies took wing, leaving the lighter colored earth exposed. The truck driver beat a hasty retreat, oblivious to the fact that his vehicle was covered with flies. The unwelcome guests stayed on for nearly a week.
Besides multitudes of flies, thousands of crows found a sumptuous feast at this garbage burial site. Eventually these birds spread out to the surrounding farms and damaged growing crops. Soon people adversely affected by the flies and the birds raised their voice in protest, demanding that no more garbage be buried in the area.
After many meetings it was resolved that the following measures be taken: (1) Find other areas in which to bury the garbage, (2) take steps to reduce the garbage, and (3) build a new incinerator to burn all the combustible garbage into ashes. There was no difficulty in finding more land for garbage burial purposes. But how could the amount of garbage in a growing city be reduced?
Reducing the Garbage
The inhabitants were asked to divide their garbage into three distinct categories: (1) Combustible garbage [kitchen refuse and wastepaper]; (2) noncombustible garbage [broken china, fluorescent bulbs and plastic]; (3) recyclable garbage [metallic things, including tin cans, glass and glass bottles]. Then certain days were assigned to collect the various kinds of garbage. Because only the combustible garbage would be taken to the incinerator, the amount that had to be burned and buried was reduced.
The people of Numazu were very cooperative when the new garbage-disposal arrangement went into operation in April of 1975. A rich dividend resulted. In the fiscal year 1975, 335 tons of recyclable garbage—metals and tin cans—and 1,530 tons of glass and bottles were sold for a total of $30,280. Think of it—over $30,000 was earned from garbage!
Pollution-Free Incinerator Plant
What about the third measure—a new incinerator? Plans were made to build it right next to the existing incinerator. People living nearby, of course, were not too happy to hear of this and they protested. There were repeated meetings with neighborhood representatives, and finally a mutual understanding was reached. The most important assurance was that there would be no secondary pollution from the new incinerator.
Construction started immediately and the job was completed in June of 1976. The building is equipped with sophisticated machines, remote controls and a computer. A working force of only 30 persons is sufficient to man the entire plant. Whereas the old incinerator had a capacity of 125 tons per day, the new one can handle more than double that amount—300 tons in 24 hours.
Unloading the Garbage
Let us follow a load of garbage through this plant and observe how it is reduced to ashes.
A city truck rolls up the curved ramp and then stops on the scales to be weighed. The driver hands in a card that is inserted into the computer feed line, where the weight of the vehicle and its number are recorded automatically. The truck continues around the curve and enters the unloading area. At one of the gates, the load is dumped into the pit.
This pit is large enough to hold a week’s garbage from the city’s 202,702 inhabitants. It extends from the basement to the fifth-floor area, where two large cranes function. The cranes are operated by remote control from a special enclosed room. When a load is shoveled up, it is weighed automatically and its weight is recorded. The load then is dropped into the hopper.
Garbage to Ashes
The hopper serves as the entrance to the incinerator proper. From there the garbage is fed, little by little, into the furnace. The flow of garbage is controlled automatically by special equipment, preventing the furnace from becoming choked.
On entering the furnace, the garbage is first exposed to hot air that rises up from the lower sections of the furnace. This air has a temperature of 950 degrees Celsius (1,742 degrees Fahrenheit). Wastepaper and the like are consumed, and vegetable and fruit matter is dehydrated.
At this point the garbage, or what is left of it, starts to move down over a series of stairlike fire grates. Each grate is hinged on the outside edge and lifts 90 degrees from the rear. This arrangement makes it possible to dump everything from one grate to the next one below. It also keeps the garbage in constant agitation and assures that everything is thoroughly consumed by being evenly exposed to the air and tremendous heat. The entire process is monitored by television cameras and is watched in the central office. Finally, when the burning process is completed, the ashes fall between two rollers. Anything that has not already turned to dust and ashes (perhaps some tin cans and the like) is crushed.
If the dust and ashes had to be handled in this form, the whole plant would be covered with their film. Therefore, water is run into the areas where the dust and ashes fall. By conveyor belt the wetted substance then is transported to the ashpit. There the water is allowed to drain off. Next a remote-controlled crane loads the ashes onto trucks, to be taken to the burial grounds.
Of course, where there is combustion, gas and fumes are given off. How, then, is the pollution kept down?
Preventing Secondary Pollution
Gas is channeled by ducts to the gas-cooling chamber, where jets of water under high pressure bring the temperature down from 950 degrees Celsius (1,742 degrees Fahrenheit) to 800 degrees Celsius (1,472 degrees Fahrenheit). Then the gas is used to heat water for the workers’ showers and baths. Finally it passes through a preheater and warms the air that is sent to the furnace. By now the temperature of the gas has dropped to 300 degrees Celsius (572 degrees Fahrenheit).
After large particles are filtered in a machine called a “multicyclone,” the gas undergoes the final cleansing process. By means of static electricity, an electric dust collector removes enough contaminants from the gas to allow what remains to be released into the atmosphere through the 80-meter (262-foot) concrete chimney.
Another polluted element that must be handled is the water used for washing the trucks and the water from the ashes and the garbage itself. Though drawing water from Numazu City, the plant has its own filtering system. After being filtered and processed, the water is sent to the gas-cooling chamber. After being vaporized during the cooling process of the ultrahot gas coming from the incinerator, the water, in the form of vapor, passes out of the chimney.
What about bad odors? You might expect them to be very pronounced, but this is not the case. An air curtain shuts out the unloading area from the outside. When trucks dump garbage into the pit, powerful fans draw the air out of the pit, sending it through the preheater and on into the furnace. There a temperature of 950 degrees Celsius (1,742 degrees Fahrenheit) burns away the unpleasant stench. On account of the fans, the air pressure inside the pit is lower than that at the unloading area. The stench-laden air, therefore, cannot get out.
Of course, the equipment needed for preventing secondary pollution is very expensive. The total cost of the new incinerator plant was a fabulous $9,200,000 (2,760,000,000 yen)!
To some persons such a tremendous outlay of funds just to handle garbage may seem exorbitant. However, to those who love healthful and beautiful surroundings, this is not extravagant but is a necessity. They look forward to the time when harmful pollution will be controlled everywhere on earth and when the prime concern of all will be the welfare of humankind as a whole.
[Diagram on page 22]
(For fully formatted text, see publication)
Electric Dust Collector